One issue is how easy it is to manipulate these. I bought a class-2 (Under MA/common USA definitions, not as
@bigeman312 described. AKA - up to 20mph) recently and discovered that I could lift the pedal assist speed governor just by clicking a button in the associated app. I...shouldn't be able to do that? Like, this is low hanging fruit. I can only up it to 25mph, but I shouldn't be able to do that if my location is in MA or another state that doesn't qualify that as an ebike anymore.
The classes you described above would essentially make cargo bikes illegal in the state. I don't disagree that there's more regulation required but it needs to be thought through much more than the above, which are not at all aligned with international best practice. 100 lbs is a blatantly arbitrary threshold. The power of the bike is what matter, and to a lesser degree things like width. You can and do have a >100lbs pound bike limited to 20mph that's built to shuttle around kids, why should that be regulated like a motorcycle?